1. Field of the Invention
This disclosure relates to a positive active material layer composition for a rechargeable lithium battery and a rechargeable lithium battery using the same.
2. Description of the Related Art
Rechargeable lithium batteries have recently drawn attention as a power source for small portable electronic devices. They use an organic electrolyte and thereby have twice or more discharge voltage than that of a conventional battery using an alkali aqueous solution, and accordingly have high energy density.
For a positive active material of rechargeable lithium batteries, oxides including lithium and transition elements and being capable of intercalating and deintercalating lithium ions, and for example, LiCoO2, LiMn2O4, LiNi1-xCoxO2 (0<x<1), and the like have been used.
As for negative active materials of a rechargeable lithium battery, various carbon-based materials such as artificial graphite, natural graphite, and hard carbon, which can intercalate and deintercalate lithium ions, have been used.
On the other hand, a positive active material layer is formed by coating a positive active material layer composition including a positive active material and a binder on a current collector. When the binder is aqueous, the positive active material layer composition contains a strong base and thus, problems of corroding a current collector such as an aluminum (Al) substrate and the like, and producing H2 gas, and the formulation of pin-holes on an electrode.
In order to solve these problems, Japanese Patent No. 4114247 discloses a positive active material layer composition including MoO3 in an amount of 100 ppm to 10000 ppm based on a positive active material. However, the MoO3 may prevent corrosion of the Al substrate but has low conductivity and thus, decreases resistance of an electrode and resultantly, deteriorates charge and discharge characteristics of a lithium rechargeable battery.
In addition, Japanese Patent Laid-Open Publication No. 2010-021027 discloses a method of coating various metal oxides on an Al substrate, which necessarily needs an additional process and thus, increases the cost.